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This work presents an immersed-boundary technique for compressible, turbulent flows and applies the technique to simulate the effects of micro vortex generators in controlling oblique-shock/turbulent boundary-layer interactions. The Reynolds-averaged Navier--Stokes equations, closed using the Menter k-[omega]) turbulence model, are solved in conjunction with the immersed-boundary technique. The approach is validated by comparing solutions obtained using the immersed-boundary technique with solutions obtained on a body-fitted mesh and with experimental laser Doppler anemometry data collected at Cambridge University for Mach 2.5 flow over single micro vortex generators. Simulations of an impinging oblique-shock boundary-layer interaction at Mach 2.5 with and without micro vortex-generator flow control are also performed, considering the development of the flow in the entire wind tunnel. Comparisons are made with experimental laser Doppler anemometry data and surface-pressure measurements from Cambridge University and an analysis of the flow structure is performed. The results show that three dimensional effects initiated by the interaction of the oblique shock with the sidewall boundary layers significantly influence the flow patterns in the actual experiment. The general features of the interactions with and without the micro vortex-generator array are predicted to good accord by the Reynolds-averaged Navier-Stokes/ immersed-boundary model. DOI: 10.2514/1.40049

Simulations of compressible boundary-layer flow at three different Reynolds numbers ([Re.sub.[delta]] = 5.59 x [10.sup.4], 1.78 x [10.sup.5], and 1.58 x [10.sup.6]) are performed using a hybrid large-eddy simulation/Reynolds-averaged Navier--Stokes method. Variations in the recycling/rescaling method, the higher order extension, the choice of primitive variables, the Reynolds-averaged Navier--Stokes to large eddy simulation transition parameters, and the mesh resolution are considered in order to assess the model. The results indicate that the present model can provide good predictions of the mean-flow properties, second-moment statistics, and structural features of the boundary layers considered. Normalized turbulent statistics in the outer layer are found to be independent of Reynolds number, similar to incompressible turbulent boundary layers. DOI: 10.2514/1.41598

Simulations of Mach 5 turbulent flow over a 28-deg compression corner are performed using a hybrid large-eddy/ Reynolds-averaged Navier-Stokes method. The model captures the mean-flow structure of the interaction reasonably well, with observed deficiencies relating to an underprediction of the displacement effects of the shock-induced separation region. The computational results provide some support for a recent theory concerning theunderlying causes of low-frequency shock-wave oscillation. In the simulations, the sustained presence of a collection of streaks of fluid with lower/higher momentum than the average induces a low-frequency undulation of the separation front. Power spectra obtained at different streamwise stations are in good agreement with experimental results. Downstream of reattachment, the simulations capture a three-dimensional mean-flow structure, dominated by counter-rotating vortices that produce wide variations in the surface skin friction. Predictions of the structure of the reattaching boundary layer agree well with experimental pitot pressure measurements. In comparison with Reynolds-averaged model predictions, the hybrid large-eddy/Reynolds-averaged Navier-Stokes model predicts more amplification of the Reynolds stresses and a broadening of the Reynolds stress distribution within the boundary layer that is probably due to reattachment-shock motion.

A direct numerical simulation of turbulent flow in a square duct was performed for a Reynolds number based on bulk streamwise velocity and duct height equal to 4,440. The mechanism by which secondary flows are generated in a square duct was investigated. Two counterrotating secondary flows occur around the duct corner. These secondary flows were found to play a key role in momentum transfer between the corner and center of the duct. A conditional quadrant analysis was performed in the local maximum and minimum regions of the wall shear stress in order to characterize the pattern of the mean secondary flows. DOI: 10.1061/(ASCE)0733-9399(2007)133:2(213) CE Database subject headings: Numerical models; Simulation; Secondary flow; Reynolds number.

Direct numerical simulations of turbulent flows in a curved channel are performed. The drifting Taylor-Gortler vortices are identified by applying a conditional averaging. A new algorithm is proposed for identifying the drifting Taylor-Gortler vortices based on the wavelet transform of wall information. A continuous wavelet transform with Marr wavelets is employed to decompose the flow signals at a chosen length scale. An active cancellation is applied to attenuate the Taylor-Gortler vortices and to reduce the wall skin friction.

Drag reduction in turbulent channel and pipe flows by spanwise (circumferential) wall oscillations is studied numerically. The influence of the wall oscillation on near-wall streamwise vortices is examined. By the use of the Stokes second problem, a wall-normal distance parameter and an acceleration parameter are obtained to estimate the drag reduction rate. A simple equation is derived for expressing the drag reduction rate by spanwise wall oscillations. The relation between near-wall streamwise vortices and low- and high-speed fluids is scrutinized to extract the key parameters. The drag reduction mechanism is analyzed in terms of the attenuation of Reynolds shear stress.